ARS-IMAGO ST is an odourless citric acid solution that, once diluted, can be used as a universal stopping bath for black and white film and paper. The use of an acid stop bath is strongly recommended to stop the developing process with immediate action. The stop bath also helps to avoid contaminating the fixing agent, prolonging the action of the chemist and increasing its life. The concentrated chemist contains Citric Acid Monohydrate, which is free of PBT/vPvB chemicals.